Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 75: Metal substrates: Adsorption of organic / bio molecules VIII
O 75.4: Vortrag
Donnerstag, 17. März 2011, 15:45–16:00, PHY C213
Coverage and temperature driven isomerization of TBI on Au(111) — •Cornelius Gahl1, Daniel Brete1, Robert Carley1, Roland Schmidt1, Erik R. McNellis2, Karsten Reuter2,3, Petra Tegeder4, Johannes Mielke2, Leonhard Grill2, and Martin Weinelt1,4 — 1Max-Born-Institut, Max-Born-Str. 2a, 12489 Berlin — 2Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin — 3Technische Universität München, Lichtenbergstr. 4, 85747 Garching — 4Freie Universität Berlin, Arnimallee 14, 14195 Berlin
Tetra-tert-butyl azobenzene (TBA) is one of the few examples of molecular switches which have been successfully photoisomerized after adsorption on a metal surface. We have now studied the corresponding imine, N-(3,5-di-tert-butylbenzylidene)-3,5-di-tert-butylaniline, referred to as TBI, by core-level spectroscopy, STM and dispersion corrected DFT . Although isomerization of TBI/Au(111) could not be optically induced, the molecules can run through a complete thermally driven isomerisation cycle. At 210 K TBI adsorbs in trans-conformation. Upon annealing to 320 K a bilayer of trans-TBI is transformed into a densely packed cis-monolayer. Further heating to 420 K results in desorption of half of the molecules leaving a close-packed trans-monolayer. Experiment and theory result in a consistent picture of the molecular adsorption geometry for both isomers as well as the lateral layer structures. The isomerization reaction is governed by the activation energy as well as the interplay of adsorption energies (cis < trans) and maximal monolayer coverage (cis > trans).